Police on Wednesday confirmed preliminary suspicions that propane was the cause. Two 200-pound propane gas tanks were on the premises, but no natural gas lines were present.

On Tuesday, the entire structure was reduced to small shards of wood, plywood, drywall, insulation and other materials.

The 18-month-old boy’s parents were among four other residents who were injured. A plumber and insurance company representative visiting the home, seven police officers, two firefighters and two neighbors also were hurt.